1. Definition of the Invention
The present invention refers, in general, to apparatuses for harvesting shellfish and, more particularly, to an assembly for harvesting shellfish such as scallops and alike.
2. Description of the State of Art
As a rule, shellfish living on or in the sea bottom are harvested with the aid of draggers or the like which are dragged along the sea bottom. Such draggers or the like are provided with tines or knives reaching into the bottom, such that the tines or knives are pulled through the sea bottom. A jet of water is directed to the sea bottom, so that the soil of the sea bottom is stirred up and raised. As a result, a quantity of shellfish is disengaged. Behind the tines or the knives, in the dragger, a collecting basket is located in which the shellfish is caught, while mud, sand, sediment, undersized shellfish and the like can flow back through the basket. As a result of the water injection and the direction of the latter, a relatively large mass of sediment is flushed from the bottom. The fact that as a result of on the one hand, the pulling force applied to the dragger and, on the other hand, the force of the water jet directed approximately vertically during the harvesting operation, a buoyant force is applied to the dragger which must be compensated by the weight of the dragger.
Thus, one can conclude, that the known methods of harvesting shellfish suffer the problem of severely disturbing or destroying the shellfish beds. Such destruction of shellfish beds limits the ability of the latter to regenerate themselves, thus reducing the quantity of shellfish available for harvesting in the future.
Various attempts have been made to solve or at least to mitigate the negative aspects of the existing shellfish harvesting. Some attempts can be exemplified in the following prior art references: U.S. Patent Application Publication No. 2006/0037550 to May et al. published Feb. 23, 2006 with the title “Apparatus and method of harvesting shellfish” describes an assembly comprising a boom positioned with one end over the deck of the boat and attached with another end to a turret, and a gathering device. The latter has a rake with a plurality of spaced apart prongs to entrap shellfish. The rake contains also a spray bar with a plurality of spray ports. A hydraulic cylinder is mounted on the boom, while another hydraulic cylinder is mounted to a gathering arm. The foregoing apparatus has several important disadvantages, among which are: the depth of harvesting is limited by the length of the gathering arm and the use of hydraulic cylinders renders the apparatus relatively expensive and less reliable. Another example is: U.S. Pat. No. 5,027,533 to Holt et al. issued Jul. 2, 1991 for a “Vibratory shellfish harvesters and methods”. Basically, a Holt's harvester includes a sledge having a pair of runners designated to slide over the submarine surface of a shellfish growing substrate and a plurality of tines extending downward from the sledge for penetration into the substrate. A vibratory device is used to impart a vibratory motion to those tines, in a substantially normal direction to to the submarine surface. The vibratory device includes a rotatable, off-center mass and a hydraulic motor for rotating the mass; a shock absorber device is used to reduce vibration of the runners by the vibratory device. The solution described in this patent is an example of substrate disturbance by the plurality of tines. Moreover, the use of a vibratory device negatively affects the submarine interface between bottom sediment and the water just above it, which is a very important region of submarine water.